|
Using a two-step drawing process, we fabricate long freestanding silica wires with diameters down to 50 nm that show atomic-level surface smoothness and excellent diameter uniformity. While other researchers have synthesised nanowires with smaller diameters, previous work has not yielded such uniform and smooth structures. The length of the wires can be up to tens of millimeters, giving them an aspect ratio larger than 50,000. Light can be launched along these wires by optical evanescent coupling. The wires allow single-mode operation and have very low optical losses within the visible to near-infrared spectral range. Mechanical tests show that the wires have tensile strength in excess of 5 GPa -- stronger than spider silk. The wires are also resilient and flexible, easily bending into microscopic loops.
 |
 |
Nano-knot |
Redefining hair-thin |
Altough the diameter of the wires is smaller than the wavelength of visible light, they can still guide the light in an evanescent wave that envelops the nanowire. For a 300-nm diameter nanowire, about half of the energy of 633-nm wavelength light is carried outside the wire. These wires are therefore very sensitive to the environment and are excellent candidates for chemical and biological sensors. Also, when combined with other devices such as nanoscale lasers, the wires may provide opportunities for a variety of applications ranging from optical communications to microsurgery.
|
| Plainly Speaking | Silica — glass — fibers are widely used in optical communication, sensors and other applications. These fibers have roughly the same diameters as human hair. Device applications benefit from minimizing the width of these fibers, but fabricating low-loss optical waveguides with subwavelength diameters is challenging because of the strict requirements on surface roughness and diameter uniformity.
|
Wrapping light around a hair
|
We developed a process for fabricating silica nanowires with a diameter of only one thousandth the diameter of a hair. Although significantly narrower than the wavelength of light, these nanowires can act as "rails" for light and are promising building blocks for future microphotonic devices.
|
|
Related publications